• Nuclear Engineering and Technology
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• v.52 no.9
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• pp.1939-1944
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• 2020

Pool boiling heat transfer of a copper microporous coating was experimentally studied in borated water with a concentration of boric acid from 0.0 to 5.0 vol percent (vol%) to determine the effect of boric acid on boiling heat transfer in water. A high-temperature, thermally conductive microporous coating (HTCMC) was created by sintering copper powder with an average particle size of 67 ㎛ onto a 1 cm × 1 cm plain copper surface with a coating thickness of ~300 ㎛ within a furnace in a vacuum environment. The tests showed that the nucleate boiling heat transfer coefficient (NBHT) of HTCMC became slightly less enhanced as the concentration of boric acid increased but the NBHT coefficient values were still significantly higher than those of the plain surface. The critical heat flux (CHF) values from 0 to 1.0 vol% were maintained at ~2,000 kW/㎡, and then, they gradually decreased down to ~1,700 kW/㎡ as the concentration increased further to 5.0 vol%. It is believed that the micro-scale pores of the HTCMC were partially blocked by the high boric acid concentration during the nucleate boiling such that the small bubbles were not effectively created using the HTCMC reentrant cavities as the boric acid concentration increased.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.102-102
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• 2016

Water, which is most abundant in Earth surface and very closely related to all forms of living organisms, has a simple molecular structure but exhibits very unique physical and chemical properties. Even though tremendous effort has been paid to understand this nature's core substance, there amazingly still lefts much room for scientist to explore its novel behaviors. Especially, as the scale goes down to nano-regime, water shows extraordinary properties that are not observable in bulk state. One of such interesting features is the formation of nanoscale bubbles showing unusual long-term stability. Nanobubbles can be spontaneously formed in water on hydrophobic surface or by decompression of gas-saturated liquid. In addition, the nanobubbles can be generated during electrochemical reaction at normal hydrogen electrode (NHE), which possibly distorts the standard reduction potential at NHE as the surface nanobubble screens the reaction with electrolyte solution. However, the real-time evolution of these nanobubbles has been hardly studied owing to the lack of proper imaging tools in liquid phase at nanoscale. Here we demonstrate, for the first time, that the behaviors of nanobubbles can be visualized by in situ transmission electron microscope (TEM), utilizing graphene as liquid cell membrane. The results indicate that there is a critical radius that determines the long-term stability of nanobubbles. In addition, we find two different pathways of nanobubble growth: i) Ostwald ripening of large and small nanobubbles and ii) coalescence of similar-sized nanobubbles. We also observe that the nucleation and growth of nanoparticles and the self-assembly of biomolecules are catalyzed at the nanobubble interface. Our finding is expected to provide a deeper insight to understand unusual chemical, biological and environmental phenomena where nanoscale gas-state is involved.

• Journal of the Korean Geographical Society
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• v.1
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• pp.67-82
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• 1963

This paper examined the settlement and evolution of the Namdo Food Festival holding in Nakan folk village since 1994. The Namdo Food Festival is a representative event tourism in Chonnam which beautifully displays Nakan eup-sung's folk landscape and Namdo's traditional food, a prime tourist resource. Since 1994, the Namdo Food Festival has steadily evoloved in the scale aspects of the program budget, and the number of visitors participating in festiva. In addition, the period of the food festival was fixed for a week, early in October. The majority of visitors to the festival was from Kwangju. Moreover, visitors from other provinces have steadily increased, in particular visitors from Yeongnam province such as Pusas and Kyeongnam provinces have increased since 1996. In order to settle down and develop the Namdo Food Festival, the followings should be done change of the ownership from public to private sector, training of professional entertainers, development of programs which can reinforce historical aspects and placeness of Nakan folk village, adoption of management technoques for the local economic activities, and extension of linkage with tourists places around Nakan folk village, reflection of tourists interests and needs through a continuoua tourist's behaviour analysis.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.3
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• pp.57-68
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• 2000

The Power Augmented Ram(PAR) effect, which blows the down stream of the propellers into the underside of the wings and hence increases the pressure between the lower surface of the wings and the sea surface, is known significantly to enhance the performance of the WIG concept by reducing the take-off and landing speeds. The aerodynamic characteristics of a 20 passenger PARWIG are investigated by wind tunnel tests with the 1/20 scale model. The efflux of the forward mounted propellers are simulated by jet flows with a blower and duct system. The lift, drag, and pitch moment of the model with various ground clearances, angles of attack and flap angles are measured for the various jet velocities, jet nozzle angles, horizontal and vertical positions of the nozzle, and the nozzle diameters. The aerodynamic characteristics of the PARWIG due to these parametric changes are compared and pertinent discussions are included. It is shown that the proper use of the PAR can increase the lift coefficient of as much as up to 4.

• Journal of Korean Foot and Ankle Society
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• v.10 no.1
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• pp.37-41
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• 2006

Purpose: To investigate the early results of limited open repair technique of Achilles tendon ruptures, and to describe the surgical technique. Materials and Methods: From October 2004 to February 2005, a total of 10 patients with Achilles tendon rupture underwent limited open repair. The average age of the patients was 39.3 years, and the average follow-up period was 9 months. The causes of injury were sports injuries in 8 cases, and slip down in 2. The mean interval between the injury and the operation was 9 days. The clinical results were assessed by patient's satisfaction, incision length, hospitalization, the ankle-hindfoot scale of American Foot and Ankle Society (AOFAS), and complications. Results: Of 10 patients, 8 were very satisfied, and the remaining 2 were satisfied. The mean incision length was 2.0 cm, and the mean hospitalization was 2 days. The mean AOFAS score was 97 points, and there was no complications such as infection, rerupture, or nerve injury. All patients returned to work at approximately 2 months, and resumed light exercise such as jogging at approximately 3 months. Conclusion: Limited open repair technique of Achilles tendon ruptures is provided for better cosmetic results, high patient's satisfaction, and functionally successful results without postoperative complications.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.3
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• pp.280-288
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• 2014

SDC (Samarium doped Ceria) electrolyte was developed for Intermediate temperature SOFC ($500^{\circ}C-800^{\circ}C$) which showed a good electrical conductivity. In this study, we used sintering aids to reduce the SDC sintering temperature down to $1000^{\circ}C$, especially which can help the SOFC scale-up. In order to reduce the SDC sintering temperature, $Li_2CO_3$ and $TiO_2$ were used as a sinering aids for decreasing sintering temperature. $Li_2CO_3$ and $TiO_2$ doped SDC sintered at $1000^{\circ}C$ showed 99% of the theoretical density and higher electrical conductivity than the pure SDC sintered at $1500^{\circ}C$. When measuring the OCV (Open circuit voltage) with the $Li_2CO_3$ and $TiO_2$ doped SDC electrolyte, however, the OCV values were lower than the theoretical OCV values which means that the modified SDC still had electronic conductivity.

• Convergence Security Journal
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• v.6 no.1
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• pp.1-11
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• 2006

The exponential increase of malicious and criminal activities in cyber space is posing serious threat which could destabilize the foundation of modem information society. In particular, unexpected network paralysis or break-down created by the spread of malicious traffic could cause confusion and disorder in a nationwide scale, and unless effective countermeasures against such unexpected attacks are formulated in time, this could develop into a catastrophic condition. As a result, there has been vigorous effort and search to develop a functional state-level cyber-threat early-warning system however, the efforts have not yielded satisfying results or created plausible alternatives to date, due to the insufficiency of the existing system and technical difficulties. The existing cyber-threat forecasting and early-warning depend on the individual experience and ability of security manager whose decision is based on the limited security data collected from ESM (Enterprise Security Management) and TMS (Threat Management System). Consequently, this could result in a disastrous warning failure against a variety of unknown and unpredictable attacks. It is, therefore, the aim of this research to offer a conceptual design for "Knowledge-based Real-Time Cyber-Threat Early-Warning System" in order to counter increasinf threat of malicious and criminal activities in cyber suace, and promote further academic researches into developing a comprehensive real-time cyber-threat early-warning system to counter a variety of potential present and future cyber-attacks.

• Korean Journal of Ecology and Environment
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• v.45 no.4
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• pp.347-355
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• 2012

In this study, non-point pollution sources in the Yeongsan river basin are analyzed; then, the priority regions (areas divided on a small scale) of management are selected for efficient water management of the Seungcheon and Jooksan reservoirs, which were constructed as one of the 4 major rivers restoration projects. The priority regions are decided by using the criteria of the excessive rate of target water quality, non-point pollution load per unit area, total TP load and down flow distance. The results of this study are as follows. The upper 10% of the priority regions for non-point pollution management includes YB15, YB05, YB10, YB24, YB14 and YB11 for the Seungcheon reservoir watershed, and YC24, YC25, YC30, YC34, YC22 and YC17 for the Jooksan reservoir watershed. However, a few regions in each of the Seungcheon and Jooksan reservoirs need to be selected in higher order, and the non-point pollution removal facilities in the regions need to be installed with respect to budget, urgent matter, and so on.

• Journal of muscle and joint health
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• v.6 no.1
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• pp.7-21
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• 1999

This study attempts to provide the rudimentary data that might help patients with Rheumatoid Arthritis manage an independent life by the analysis of their activities of daily living(ADL). The subjects were forty patients who had been diagnosed Rheumatoid Arthritis and under drug therapy from RA clinics of the two university hospitals in Pusan. Data were collected by performing an individual interview for each of them during June 15th through July 15th 1998. Questionaires were imployed to investigate the general characteristics of patients. the traits of Rheumatoid Arthritis, and actual conditions of their activities of daily living. The questionaires utilized especially for the study of ADL is the version of Lee Eun Ok's tool which modified and complemented Katz scale (Katz, Down, Cogh and Grots 1970) and Bathel index(Bathel. 1973). It's consisted of 31 questions that each question is measured by 0-3points. The high score in the questionaire signifies the high independency in the ADL. The data were analyzed by SPSS/Win in terms of frequency, percentage, mean, and standard deviation, close connection with the contents of the personal interview. Total mean of the ADL shows $1.55{\pm}0.68$, indicating the overall activities of daily living is generally dependent. It also indicates that patients, in the condition of dependent activity. tends either to have recourse to drugs or to take negative strategy, getting help from inside or outside family member. Hence, it is necessary that patients are exposed to the introduction and instruction of self-help devies that might help them manage a comparatively independent ADL, easing their paychological burden.

• Journal of Korea Water Resources Association
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• v.45 no.11
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• pp.1121-1130
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• 2012

Projected changes and their impacts on water quality are simulated in response to climate change stressors. CGHR (T63) simulation on the A1B scenario is converted to regional scale data using a statistical down-scaling method and applied to SWAT model to assess water quality impacts in Nakdong River basin. The results demonstrate that rainfall-runoff and pollutant loading in the future (2011~2100) will clearly increase as compared to the last 30-year average. The rate of pollutant loading increase is expected to continue its acceleration until 2040s. Runoff also shows similar patterns to the precipitation, increasing by 60%. Accordingly, the runoff increase results in escalation of pollutant loading by 35~45% for TSS and 5~20% for T-P. This phenomenon is more pronounced in the upper basin during winter and spring season.